From 96217d357f2ed470ff2136bffdc2700ccf21f07b Mon Sep 17 00:00:00 2001
From: Frank Emrich <emrich@google.com>
Date: Mon, 15 Mar 2021 23:47:31 +0100
Subject: [PATCH] [compiler] Emit vpbroadcastb for I8x16Splat on x64 if
 supported

Change-Id: Iec90b4821f41838eb4c2bae26035af4e30082ef9
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2762140
Reviewed-by: Zhi An Ng <zhin@chromium.org>
Commit-Queue: Frank Emrich <emrich@google.com>
Cr-Commit-Position: refs/heads/master@{#73428}
---
 .../backend/x64/code-generator-x64.cc         | 22 ++++++++++++++-----
 1 file changed, 17 insertions(+), 5 deletions(-)

diff --git a/src/compiler/backend/x64/code-generator-x64.cc b/src/compiler/backend/x64/code-generator-x64.cc
index f8e38939d2..575a15d408 100644
--- a/src/compiler/backend/x64/code-generator-x64.cc
+++ b/src/compiler/backend/x64/code-generator-x64.cc
@@ -3352,13 +3352,25 @@ CodeGenerator::CodeGenResult CodeGenerator::AssembleArchInstruction(
     }
     case kX64I8x16Splat: {
       XMMRegister dst = i.OutputSimd128Register();
-      if (HasRegisterInput(instr, 0)) {
-        __ Movd(dst, i.InputRegister(0));
+      if (CpuFeatures::IsSupported(AVX2)) {
+        CpuFeatureScope avx_scope(tasm(), AVX);
+        CpuFeatureScope avx2_scope(tasm(), AVX2);
+        if (HasRegisterInput(instr, 0)) {
+          __ vmovd(kScratchDoubleReg, i.InputRegister(0));
+          __ vpbroadcastb(dst, kScratchDoubleReg);
+        } else {
+          __ vpbroadcastb(dst, i.InputOperand(0));
+        }
       } else {
-        __ Movd(dst, i.InputOperand(0));
+        if (HasRegisterInput(instr, 0)) {
+          __ Movd(dst, i.InputRegister(0));
+        } else {
+          __ Movd(dst, i.InputOperand(0));
+        }
+        __ Xorps(kScratchDoubleReg, kScratchDoubleReg);
+        __ Pshufb(dst, kScratchDoubleReg);
       }
-      __ Xorps(kScratchDoubleReg, kScratchDoubleReg);
-      __ Pshufb(dst, kScratchDoubleReg);
+
       break;
     }
     case kX64Pextrb: {